自定义添加配置文件节点

            // Get the application configuration file.
            Configuration config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
            string sectionName = "appSettings";

            // Add an entry to appSettings.
            int appStgCnt = ConfigurationManager.AppSettings.Count;
            string newKey = "NewKey" + appStgCnt.ToString();

            string newValue = DateTime.Now.ToLongDateString() + " " + DateTime.Now.ToLongTimeString();
            config.AppSettings.Settings.Add(newKey, newValue);

            // Save the configuration file.
            config.Save(ConfigurationSaveMode.Modified);

            // Force a reload of the changed section. This 
            // makes the new values available for reading.
            ConfigurationManager.RefreshSection(sectionName);

            // Get the AppSettings section.
            AppSettingsSection appSettingSection = (AppSettingsSection)config.GetSection(sectionName);

            Console.WriteLine();
            Console.WriteLine("Using GetSection(string).");
            Console.WriteLine("AppSettings section:");
            Console.WriteLine(appSettingSection.SectionInformation.GetRawXml());
            Console.ReadLine();